As a dryer which dries processing materials such as coals or ores, a steam tube dryer (which is referred to as “STD”, hereinafter), a coal-in-tube (Patent Document 1), a rotary kiln, and the like are often used. The aforementioned coals or ores are used as raw materials for iron making or refining, fuel for power generation, and the like, and since it is demanded to process a mass of the coals or ores in a stable manner, the above-described respective dryers have been employed as dryers which fulfill the demand.
The STD indirectly heats the processing materials, so that a thermal efficiency is high, and a processing amount per unit volume is also large. Further, it is also possible to increase a size of the STD, so that the STD fulfills the demand regarding mass processing.
The coal-in-tube also indirectly heats the processing materials, so that a thermal efficiency is high, and a processing amount per unit volume is also large, in a similar manner to the aforementioned STD. However, there is a disadvantageous point that a size thereof is difficult to be increased, when compared to the STD. For example, when an amount capable of being processed by one STD described above is tried to be processed by the coal-in-tube, a plurality of the coal-in-tubes are sometimes required.
The rotary kiln applies hot air to the processing materials to directly dry the processing materials, and thus it has a disadvantageous point that a heat efficiency is lower than that provided by the indirect heating. Further, there is also a disadvantageous point that an exhaust gas processing facility becomes very large. From the reasons as described above, the STD has precedence as the dryer which processes a mass of processing materials.